Flame retardant resin composition and cable using the same

ABSTRACT

In a flame retardant resin composition containing a polyolefin resin, a silicone-based compound blended at a ratio of 1.5 parts by mass or more and 20 parts by mass or less relative to 100 parts by mass of the polyolefin resin, a fatty acid containing compound blended at a ratio of 5 parts by mass or more and 20 parts by mass or less relative to 100 parts by mass of the polyolefin resin, and an inorganic flame retardant blended at a ratio of 5 parts by mass or more and 40 parts by mass or less relative to 100 parts by mass of the polyolefin resin, the decomposition onset temperature of the inorganic flame retardant is lower than the decomposition onset temperature of the silicone-based compound.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a National Stage of International Application No.PCT/JP2014/081971 filed Dec. 3, 2014, claiming priority based onJapanese Patent Application No. 2013-251231 filed Dec. 4, 2013, thecontents of all of which are incorporated herein by reference in theirentirety.

TECHNICAL FIELD

The present invention relates to a flame retardant resin composition anda cable using the composition.

BACKGROUND ART

As a flame retardant resin composition, there is known a compositionformed by adding metal hydroxide as a flame retardant to a polyolefinresin, and also adding a silicone-based compound such as silicone oil,or magnesium stearate as a flame retardant aid, for example (see PatentDocument 1 described below).

CITATION LIST Patent Document

-   Patent Document 1: JPH10-7913 A

SUMMARY OF THE INVENTION Problem to be Solved by the Invention

However, there is a case in which flame retardancy is not obtained atsufficient level with the composition described in Patent Document 1.Here, when the addition amount of the flame retardant is increased,flame retardancy can be improved. However, in this case, the mechanicalproperty of the composition is deteriorated.

Therefore, there has been a demand for a flame retardant resincomposition that can secure excellent flame retardancy while securing anexcellent mechanical property.

The invention was achieved under such circumstances, and it is an objectof the invention to provide a flame retardant resin composition whichcan secure excellent flame retardancy while securing an excellentmechanical property, and a cable using this resin composition.

Means for Solving Problem

In order to solve the problems described above, the present inventorsstudied the magnitude relationship between the decomposition onsettemperature of metal hydroxide as a flame retardant and thedecomposition onset temperature of a silicone-based compound. As aresult, the inventors found that when a silicone-based compound, a fattyacid containing compound such as magnesium stearate, and an inorganicflame retardant such as metal hydroxide or the like are respectivelyblended at a predetermined ratio relative to 100 parts by mass of apolyolefin resin, the problems can be solved by adjusting thedecomposition onset temperature of an inorganic flame retardant to belower than the decomposition onset temperature of a silicone-basedcompound, and thus the inventors completed the invention.

Namely, the invention relates to a flame retardant resin compositioncontaining a polyolefin resin, a silicone-based compound blended at aratio of 1.5 parts by mass or more and 20 parts by mass or less relativeto 100 parts by mass of the polyolefin resin, a fatty acid containingcompound blended at a ratio of 5 parts by mass or more and 20 parts bymass or less relative to 100 parts by mass of the polyolefin resin, andan inorganic flame retardant blended at a ratio of 5 parts by mass ormore and 40 parts by mass or less relative to 100 parts by mass of thepolyolefin resin, in which the decomposition onset temperature of theinorganic flame retardant is lower than the decomposition onsettemperature of the silicone-based compound.

According to the flame retardant resin composition of the invention,excellent flame retardancy can be secured with an excellent mechanicalproperty secured.

Meanwhile, the present inventors assume that the reason why moreexcellent flame retardancy can be obtained with the flame retardantresin composition of the invention is as follows.

That is, as the decomposition onset temperature of an inorganic flameretardant is lower than the decomposition onset temperature of asilicone-based compound, at the time of combustion, the inorganic flameretardant is decomposed by heat before the silicone-based compound isdecomposed by heat. The decomposition of the inorganic flame retardantat this time is considered to be an endothermic reaction. Accordingly,the temperature increase of a polyolefin resin is sufficientlysuppressed and it becomes possible to inhibit continuous combustion.Furthermore, once a silicone-based compound is decomposed by heat, abarrier layer of a silicone-based compound is formed on a surface of thepolyolefin resin. The present inventors assume that a flame retardanteffect is enhanced based on such reasons.

In the above flame retardant resin composition, the inorganic flameretardant is preferably aluminum hydroxide.

In this case, more excellent flame retardancy can be obtained comparedto a case in which the inorganic flame retardant is an inorganic flameretardant other than aluminum hydroxide.

Furthermore, in the flame retardant resin composition, the inorganicflame retardant is preferably blended at a ratio of 10 parts by mass ormore and 25 parts by mass or less relative to 100 parts by mass of thepolyolefin resin.

In this case, the flame retardancy of the flame retardant resincomposition can be more improved compared to a case in which theblending amount of the inorganic flame retardant is not within theaforementioned range.

In the above flame retardant resin composition, the fatty acidcontaining compound is preferably magnesium stearate or calciumstearate.

In this case, more excellent flame retardancy can be obtained comparedto a case in which the fatty acid containing compound is not any one ofmagnesium stearate and calcium stearate.

The flame retardant resin composition may be composed of the polyolefinresin, the silicone-based compound, the fatty acid containing compound,the inorganic flame retardant, and at least one additive selected fromthe group consisting of an oxidation inhibitor, an ultraviolet raydeterioration inhibitor, a processing aid, a coloring agent, and ananti-static agent.

In this case, the flame retardant resin composition is composed only ofthe polyolefin resin, the silicone-based compound, the fatty acidcontaining compound, the inorganic flame retardant, and at least oneadditive selected from the group consisting of the oxidation inhibitor,the ultraviolet ray deterioration inhibitor, the processing aid, thecoloring agent, and the anti-static agent.

In the flame retardant resin composition, it is preferable that theoxidation inhibitor is composed of at least one selected from the groupconsisting of a phenol-based oxidation inhibitor, an amine-basedoxidation inhibitor, a sulfur-based oxidation inhibitor, aphosphorus-based oxidation inhibitor, a hydrazine-based oxidationinhibitor, an amide-based oxidation inhibitor, phosphoric acid, andcitric acid, the ultraviolet ray deterioration inhibitor is composed ofat least one selected from the group consisting of a benzophenone-basedultraviolet ray deterioration inhibitor, a salicylate-based ultravioletray deterioration inhibitor, a benzotriazole-based ultraviolet raydeterioration inhibitor, an acrylonitrile-based ultraviolet raydeterioration inhibitor, a metal complex salt-based ultraviolet raydeterioration inhibitor, and a hindered amine-based ultraviolet raydeterioration inhibitor, the processing aid is composed of at least oneselected from the group consisting of a hydrocarbon-based processingaid, a fatty acid-based processing aid, a fatty acid amide-basedprocessing aid, an ester-based processing aid, an alcohol-basedprocessing aid, a metal soap, and wax, the coloring agent is composed ofat least one selected from the group consisting of an inorganic pigment,an organic pigment, a dye, and carbon black, and the anti-static agentis composed of at least one selected from the group consisting of acationic active agent, an anionic active agent, a non-ionic activeagent, and an amphoteric active agent.

The invention is also a cable comprising an insulated wire which has aconductor and an insulating layer covering the conductor, in which theinsulating layer consists of the aforementioned flame retardant resincomposition.

The invention is also a cable having a conductor, an insulating layercovering the conductor, and a sheath covering the insulating layer, inwhich at least one of the insulating layer and the sheath consists ofthe aforementioned flame retardant resin composition.

The invention is also a cable having a sheath and an optical fiberprovided on the inner side of the sheath or provided to penetrate thesheath, in which the sheath consists of the aforementioned flameretardant resin composition.

Meanwhile, in the invention, the decomposition onset temperature meansdecomposition onset temperature which is determined according toanalysis of gas evolved from the flame retardant resin composition ofthe invention based on evolved gas analysis (EGA-MS) method.Specifically, when an EGA thermogram is measured at the followingconditions by using a thermal analysis and gas chromatograph-massspectrometry (trade name: “GCMS-QP2010”, manufactured by ShimadzuCorporation) in which a sample loading part equipped with a thermaldecomposition device (pyrolyzer) and a gas chromatograph-massspectrometry are connected to each other via a capillary tube made ofSUS (trade name: “Ultra ALLOY-DTA”, manufactured by FrontierLaboratories Ltd., inner diameter of 0.15 mm and length of 2.5 m), thedecomposition onset temperature refers to the temperature whichcorresponds to a peak rising point with respect to a baseline in thethermogram.

<Conditions>

Temperature increasing rate in thermal decomposition device: 50° C./min

Temperature range: 70 to 700° C.

Column oven temperature: 320° C.

Carrier gas: helium

Pressure: 90.0 kPa

Column flow rate: 0.92 mL/min

Effect of the Invention

According to the invention, a flame retardant resin composition whichcan secure excellent flame retardancy while securing an excellentmechanical property, and a cable using the composition are provided.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a partial side view illustrating a first embodiment of thecable of the invention;

FIG. 2 is a cross-sectional view taken along the line II-II illustratedin FIG. 1;

FIG. 3 is a cross-sectional view illustrating a second embodiment of thecable of the invention; and

FIG. 4 is a cross-sectional view illustrating a third embodiment of thecable of the invention.

MODE(S) FOR CARRYING OUT THE INVENTION

Hereinbelow, a first embodiment of the invention is described in detailusing FIG. 1 and FIG. 2.

[Cable]

FIG. 1 is a partial side view illustrating the first embodiment of thecable according to the invention. FIG. 2 is a cross-sectional view takenalong the II-II line illustrated in FIG. 1. As illustrated in FIG. 1 andFIG. 2, a cable 10 comprises one insulated wire 4, and a sheath 3 thatcovers the one insulated wire 4. The insulated wire 4 has an internalconductor 1 and an insulating layer 2 that covers the internal conductor1.

Herein, the insulating layer 2 and the sheath 3 consist of a flameretardant resin composition, and this flame retardant resin compositioncontains a polyolefin resin, a silicone-based compound blended at aratio of 1.5 parts by mass or more and 20 parts by mass or less relativeto 100 parts by mass of the polyolefin resin, a fatty acid containingcompound blended at a ratio of 5 parts by mass or more and 20 parts bymass or less relative to 100 parts by mass of the polyolefin resin, andan inorganic flame retardant blended at a ratio of 5 parts by mass ormore and 40 parts by mass or less relative to 100 parts by mass of thepolyolefin resin. Herein, the decomposition onset temperature of theinorganic flame retardant is lower than the decomposition onsettemperature of the silicone-based compound.

The insulating layer 2 and the sheath 3 that are formed of theaforementioned flame retardant resin composition can secure excellentflame retardancy while securing an excellent mechanical property.Accordingly, the cable 10 can secure excellent flame retardancy whilesecuring an excellent mechanical property.

[Method for Producing Cable]

Next, a method for producing the aforementioned cable 10 is described.

(Conductor)

First, the internal conductor 1 is prepared. The internal conductor 1may be composed of a single strand, or may be composed of plural strandsthat are bundled together. Furthermore, the internal conductor 1 is notparticularly limited in terms of the diameter of the conductor, thematerial of the conductor and the like, and it can be appropriatelyselected in accordance with the use.

(Flame Retardant Resin Composition)

Meanwhile, the aforementioned flame retardant resin composition isprepared. The flame retardant resin composition contains a polyolefinresin, a silicone-based compound blended at a ratio of 1.5 parts by massor more and 20 parts by mass or less relative to 100 parts by mass ofthe polyolefin resin, a fatty acid containing compound blended at aratio of 5 parts by mass or more and 20 parts by mass or less relativeto 100 parts by mass of the polyolefin resin, and an inorganic flameretardant blended at a ratio of 5 parts by mass or more and 40 parts bymass or less relative to 100 parts by mass of the polyolefin resin.

(Polyolefin Resin)

As described above, examples of the polyolefin resin include anethylene-based resin and a propylene-based resin. It may be used eithersingly or as a mixture of two or more thereof. Herein, theethylene-based resin refers to a resin which contains ethylene as aconstitutional unit and examples of the ethylene-based resin include apolyethylene resin (PE), an ethylene ethyl acrylate copolymer (EEA), andan ethylene vinyl acetate copolymer (EVA). Furthermore, thepropylene-based resin refers to a resin which contains propylene as aconstitutional unit and examples of the propylene-based resin include apolypropylene resin (PP).

(Silicone-Based Compound)

The silicone-based compound is a compound which functions as a flameretardant aid. Examples of the silicone-based compound includepolyorganosiloxanes. Here, the polyorganosiloxanes are compounds whichhave siloxane bonds as a main chain, and have organic groups in sidechains. Examples of the organic groups include a methyl group, a vinylgroup, an ethyl group, a propyl group, and a phenyl group. Specificexamples of the polyorganosiloxanes include dimethylpolysiloxane,methylethylpolysiloxane, methyloctylpolysiloxane,methylvinylpolysiloxane, methylphenylpolysiloxane, andmethyl-(3,3,3-trifluoropropyl)polysiloxane. Examples ofpolyorganosiloxane include silicone powder, silicone gum, and siliconeresin. Among them, silicone gum is preferable. In this case, bloomingdoes not easily occur.

The silicone-based compound is blended at a ratio of 1.5 parts by massor more and 20 parts by mass or less relative to 100 parts by mass ofthe polyolefin resin as described above.

When the ratio of the silicone-based compound is less than 1.5 parts bymass relative to 100 parts by mass of the polyolefin resin, the flameretardancy is significantly lowered.

Furthermore, when the blending ratio of the silicone-based compound ismore than 20 parts by mass relative to 100 parts by mass of thepolyolefin resin, blooming may easily occur.

The silicone-based compound is preferably blended at a ratio of 15 partsby mass or less. In this case, a more excellent mechanical property canbe obtained compared to a case in which the ratio of the silicone-basedcompound is more than 15 parts by mass.

The silicone-based compound may be attached in advance to the surface ofthe inorganic flame retardant. In this case, it is preferable that theentirety of each of the inorganic flame retardant included in the flameretardant resin composition be covered with the silicone-based compound.In this case, since the inorganic flame retardant can be easilydispersed in the polyolefin resin, uniformity of the characteristics inthe flame retardant resin composition is further improved.

Examples of the method of attaching the silicone-based compound to thesurface of the inorganic flame retardant include, for example, a methodin which the silicone-based compound is added to the inorganic flameretardant, they are mixed to obtain a mixture, the mixture is thensubsequently dried at 40° C. to 75° C. for 10 minutes to 40 minutes, andthe dried mixture is pulverized using a Henschel mixer, an atomizer orthe like.

Meanwhile, the decomposition onset temperature (T1) of thesilicone-based compound is preferably lower than the decomposition onsettemperature (T2) of the polyolefin resin. In this case, an advantage ofhaving more excellent flame retardancy is obtained compared to a case inwhich T1 is the same or higher than T2.

The (T2−T1) is not particularly limited if it is higher than 0° C., butit is preferably 100 to 250° C. In this case, an advantage of havingmore excellent flame retardancy is obtained compared to a case in whichthe (T2−T1) is not within the aforementioned range. The (T2−T1) is morepreferably 150 to 200° C.

(Fatty Acid Containing Compound)

The fatty acid-containing compound is a compound which functions as aflame retardant aid. The fatty acid-containing compound refers to acompound containing a fatty acid or a metal salt thereof. Here, as thefatty acid, for example, a fatty acid having 12 to 28 carbon atoms isused. Examples of such a fatty acid include lauric acid, myristic acid,palmitic acid, stearic acid, tuberculostearic acid, oleic acid, linoleicacid, arachidonic acid, behenic acid, and montanic acid. Among them, thefatty acid is preferably stearic acid or tuberculostearic acid. Stearicacid is particularly preferred. In this case, more excellent flameretardancy is obtained as compared to a case in which a fatty acid otherthan stearic acid or tuberculostearic acid is used.

Examples of the metal that constitutes a metal salt of the fatty acidinclude magnesium, calcium, zinc, and lead. The metal salt of the fattyacid is preferably magnesium stearate or calcium stearate. In this case,more excellent flame retardancy is obtained as compared to a case inwhich a fatty acid containing compound is not either magnesium stearateor calcium stearate.

The fatty acid containing compound is blended at a ratio of 5 parts bymass or more and 20 parts by mass or less relative to 100 parts by massof the polyolefin resin as described above.

When the ratio of the fatty acid containing compound is less than 5parts by mass, the flame retardancy is significantly lowered.

When the blending ratio of the fatty acid containing compound is morethan 20 parts by mass relative to 100 parts by mass of the polyolefinresin, blooming may easily occur.

The fatty acid containing compound is preferably blended at a ratio of15 parts by mass or less. In this case, a more excellent mechanicalproperty can be obtained compared to a case in which the ratio of thefatty acid containing compound is more than 15 parts by mass.

(Inorganic Flame Retardant)

The inorganic flame retardant is not particularly limited if it is aninorganic flame retardant which has lower decomposition onsettemperature (T3) than the decomposition onset temperature (T1) of thesilicone-based compound.

When T1−T3 is 0° C. or lower, the flame retardancy is significantlylowered.

Examples of the inorganic flame retardant include aluminum hydroxide andcalcium aluminate hydrate. In particular, aluminum hydroxide ispreferable. In this case, more excellent mechanical property is obtainedcompared to a case in which the inorganic flame retardant is aninorganic flame retardant other than aluminum hydroxide.

The (T1−T3) is not particularly limited if it is higher than 0° C., butit is preferably 50 to 250° C. In this case, an advantage of having moreexcellent flame retardancy is obtained compared to a case in which the(T1−T3) is not within the aforementioned range. The (T1−T3) is morepreferably 50 to 150° C.

The inorganic flame retardant is blended at a ratio of 5 parts by massor more and 40 parts by mass or less relative to 100 parts by mass ofthe polyolefin resin.

In this case, more significantly improved flame retardancy is obtainedcompared to a case in which the blending ratio of the inorganic flameretardant is more than 40 parts by mass relative to 100 parts by mass ofthe polyolefin resin. On the other hand, the flame retardancy issignificantly improved compared to a case in which the blending ratio ofthe inorganic flame retardant is less than 5 parts by mass relative to100 parts by mass of the polyolefin resin.

Furthermore, it is preferable that the inorganic flame retardant isblended at a ratio of 10 parts by mass or more and 25 parts by mass orless relative to 100 parts by mass of the polyolefin resin. In thiscase, the flame retardancy of the flame retardant resin composition canbe improved more compared to a case in which the blending amount of theinorganic flame retardant is not within the aforementioned range.

(Additives)

The flame retardant resin composition may also contain an additive, ifnecessary. The additive is composed of a material which is differentfrom the polyolefin resin, silicone-based compound, fatty acidcontaining compound, and inorganic flame retardant that are describedabove. Examples of the additive include an oxidation inhibitor, anultraviolet ray deterioration inhibitor, a processing aid, a coloringagent, and an anti-static agent. They may be used either singly or incombination of two or more types. Herein, any one of an oxidationinhibitor, an ultraviolet ray deterioration inhibitor, a processing aid,a coloring agent, and an anti-static agent refers to an additive whichdoes not improve the flame retardancy of the flame retardant resincomposition as it is contained in the flame retardant resin compositiondescribed above. Herein, the expression “which does not improve theflame retardancy of the flame retardant resin composition” means that,when a flame retardant resin composition containing an oxidationinhibitor, an ultraviolet ray deterioration inhibitor, a processing aid,a coloring agent, or an anti-static agent is tested by single verticalwire combustion test that is used for evaluation of flame retardancy ofa flame retardant resin composition in Examples and Comparative Examplesdescribed later, the test result is the same or inferior to theevaluation result of flame retardancy of a flame retardant resincomposition which is different only in that it does not contain any oneof an oxidation inhibitor, an ultraviolet ray deterioration inhibitor, aprocessing aid, a coloring agent, and an anti-static agent.

Examples of the oxidation inhibitor include a phenol-based oxidationinhibitor, an amine-based oxidation inhibitor, a sulfur-based oxidationinhibitor, a phosphorus-based oxidation inhibitor, a hydrazine-basedoxidation inhibitor, an amide-based oxidation inhibitor, phosphoricacid, and citric acid. They may be used either singly or in combinationof two or more types. Herein, the phenol-based oxidation inhibitor isparticularly preferred as an oxidation inhibitor.

Examples of the ultraviolet ray deterioration inhibitor include abenzophenone-based ultraviolet ray deterioration inhibitor, asalicylate-based ultraviolet ray deterioration inhibitor, abenzotriazole-based ultraviolet ray deterioration inhibitor, anacrylonitrile-based ultraviolet ray deterioration inhibitor, a metalcomplex salt-based ultraviolet ray deterioration inhibitor, and ahindered amine-based ultraviolet ray deterioration inhibitor. They maybe used either singly or in combination of two or more types. Herein,the hindered amine-based ultraviolet ray deterioration inhibitor isparticularly preferred as an ultraviolet ray deterioration inhibitor.

Examples of the processing aid include a hydrocarbon-based processingaid, a fatty acid-based processing aid, a fatty acid amide-basedprocessing aid, an ester-based processing aid, an alcohol-basedprocessing aid, a metal soap, and wax. They may be used either singly orin combination of two or more types. Herein, the hydrocarbon-basedprocessing aid is particularly preferred as a processing aid.

Examples of the coloring agent include an inorganic pigment, an organicpigment, a dye, and carbon black. They may be used either singly or incombination of two or more types. Herein, the inorganic pigment isparticularly preferred as a coloring agent.

Examples of the inorganic pigment include a chromate salt, a ferrocyancompound, a sulfide compound, an oxide compound, a sulfate salt, asilicate salt, a carbonate salt, and a phosphate salt. They may be usedeither singly or in combination of two or more types.

Examples of the organic pigment include an azo-based pigment, aphthalocyanin-based pigment, a vat dye-based pigment, a lake-basedpigment for dyeing, a quinacridone-based pigment, and a dioxazine-basedpigment. They may be used either singly or in combination of two or moretypes.

Examples of the dye include an anthraquinone-based dye, anindigoid-based dye, and an azo-based dye. They may be used either singlyor in combination of two or more types.

Examples of the anti-static agent include a cationic active agent, ananionic active agent, a non-ionic active agent, and an amphoteric activeagent. They may be used either singly or in combination of two or moretypes. The cationic active agent is particularly preferred as theanti-static agent.

Examples of the cationic active agent include a primary amine salt,tertiary amine, a quaternary ammonium compound, and a pyridinederivative. They may be used either singly or in combination of two ormore types.

Examples of the anionic active agent include sulfated oil, soap,sulfated ester oil, sulfated amide oil, sulfated ester, sulfonate, andphosphoric acid ester. They may be used either singly or in combinationof two or more types.

Examples of the non-ionic active agent include polyhydric alcohol fattyacid ester and ethylene oxide adduct. They may be used either singly orin combination of two or more types.

Examples of the amphoteric active agent include a carboxylic acidderivative and an imidazoline derivative. They may be used either singlyor in combination of two or more types.

The blending amount of the additive relative to 100 parts by mass of thepolyolefin resin is not particularly limited. However, it is preferably2 parts by mass or less, and more preferably 1 part by mass or less.However, the blending amount of the additive is preferably 0.1 part bymass or more relative to 100 parts by mass of the polyolefin resin.

The flame retardant resin composition can be obtained by kneading thepolyolefin resin, the inorganic flame retardant, the silicone-basedcompound, the fatty acid containing compound and the like. Kneading canbe carried out by using, for example, a kneading device such as aBanbury mixer, a tumbler, a pressurized kneader, a kneader extruder, atwin screw extruder, a mixing roll or the like. At this time, from theviewpoint of improving the dispersion property of the silicone-basedcompound, a master batch (MB) obtained by kneading a portion of thepolyolefin resin and the silicone-based compound may be kneaded with theremaining polyolefin resin, the inorganic flame retardant, the fattyacid containing compound, and the like.

Next, the internal conductor 1 is covered with the aforementioned flameretardant resin composition. Specifically, the flame retardant resincomposition described above is melt kneaded by using an extruder, and atube-shaped extrusion product is formed. Then, this tube-shapedextrusion product is continuously coated on the internal conductor 1.Thus, the insulated wire 4 is obtained.

(Sheath)

Finally, one insulated wire 4 obtained as described above is prepared,and this insulated wire 4 is coated with the sheath 3 which has beenproduced by using the flame retardant resin composition described above.The sheath 3 protects the insulating layer 2 from physical or chemicaldamage.

Thus, a cable 10 is obtained.

The invention is not limited to the first embodiment described above.For example, in the above first embodiment, the cable 10 has oneinsulated wire 4; however, the cable of the invention is not limited toa cable which has only one insulated wire 4, and the cable may have twoor more insulated wires 4 on the inner side of the sheath 3.Furthermore, a resin section formed of polypropylene or the like mayalso be provided between the sheath 3 and the insulated wire 4.

Furthermore, in the above first embodiment, the insulating layer 2 andthe sheath 3 of the insulated wire 4 are formed of the flame retardantresin composition, but it is also possible that the insulating layer 2is formed of a typical insulating resin, and only the sheath 3 is formedof the flame retardant resin composition that constitutes the insulatinglayer 2.

Furthermore, although the flame retardant resin composition of theinvention is applied to the insulating layer 2 and the sheath 3 of theinsulated wire 4 in the aforementioned first embodiment, the flameretardant resin composition of the invention can be applied to a sheathof an optical fiber cable, that is, a sheath of a cable which has asheath and an optical fiber provided on the inner side of the sheath orprovided to penetrate the sheath. Herein, examples of the optical fibercable include a drop type optical fiber cable, an indoor type opticalfiber cable, a layer type optical fiber cable, a tape slot type opticalfiber cable and the like.

FIG. 3 is a cross-sectional view illustrating an indoor type opticalfiber cable. As shown in FIG. 3, an indoor type optical fiber cable 20is provided with two tension members 22 and 23, an optical fiber 24, anda sheath 25 covering them. Herein, the optical fiber 24 is provided topenetrate the sheath 25.

FIG. 4 is a cross-sectional view illustrating a layer type optical fibercable. As shown in FIG. 4, a layer type optical fiber cable 30 isprovided with a core part 31 and a sheath 35 provided to surround thecore part 31. The core part 31 is provided with a tension member 32, arip cord 33 provided to surround the tension member 32, and an opticalfiber unit 34 which is arranged, between the tension member 32 and therip cord 33, along the longitudinal direction of the tension member 32.Herein, the optical fiber unit 34 is formed by disposing the opticalfiber 24 on the inner side of a tube 36 which is either colored ornon-colored. Accordingly, the optical fiber 24 is provided on the innerside of the sheath 35. Meanwhile, a press winding tape 37 is generallywound around the core part 31. However, the layer type optical fibercable 30 may not have the press winding tape 37. Furthermore, awater-proofing material 38 may also be filled around the optical fiberunit 34 between the rip cord 33 and the tension member 32.

In the aforementioned optical fiber cable, the sheath 25 and the sheath35 consist of the flame retardant resin composition of the invention.

EXAMPLES

Hereinbelow, the contents of the invention are more specificallydescribed by way of Examples and Comparative Examples, but the inventionis not limited to the following Examples.

Examples 1 to 14 and Comparative Examples 1 to 7

A base resin, a silicone master batch (silicone MB), a fatty acidcontaining compound, and an inorganic flame retardant were blended inthe blending amounts indicated in Tables 1 to 5, and they were kneadedfor 15 minutes at 160° C. by a Banbury mixer. Thus, a flame retardantresin composition was obtained. Meanwhile, in Tables 1 to 5, the unit ofthe blending amount of each of the blended components is parts by mass.Furthermore, in Tables 1 to 5, the blending amount of a polyethyleneresin (PE), an ethylene ethyl acrylate copolymer (EEA), an ethylenevinyl acetate copolymer (EVA), or a polypropylene resin (PP) is not 100parts by mass. However, since the resin is also included in the siliconeMB, the total amount of the base resin becomes 100 parts by mass whenthe resin in silicone MB is added with PE, EEA, EVA, or PP. Furthermore,in Tables 1 to 5, the decomposition onset temperature of the inorganicflame retardant (T3), the decomposition onset temperature of thesilicone-based compound (T1), and the decomposition onset temperature ofthe base resin (T2) are also indicated.

As the base resin, the silicone MB, the fatty acid containing compound,and the inorganic flame retardant, specifically those described belowwere used.

(1) Base resin

(A) Polyethylene resin (PE) (trade name: “EXCELLEN GMH GH030”,manufactured by Sumitomo Chemical Company, Limited)

(B) Ethylene ethyl acrylate copolymer (EEA, trade name: “DPDJ-6503”,manufactured by Nippon Unicar Company Limited)

(C) Ethylene vinyl acetate copolymer (EVA, trade name: “Evaflex V5274”,manufactured by DUPONT-MITSUI POLYCHEMICALS CO., LTD.)

(D) Polypropylene resin (PP, trade name: “E111G”, manufactured by PrimePolymer Co., Ltd.)

(2) Silicone MB (trade name: “X-22-2125H”, manufactured by Shin-EtsuChemical Co., Ltd.) containing 50% by mass of silicone gum and 50% bymass of PE

(3) Fatty acid containing compound

Mg stearate (trade name: “AFCO CHEM MGS”, manufactured by ADEKACORPORATION)

Ca stearate (trade name: “SC-P”, manufactured by Sakai Chemical IndustryCo., Ltd.)

(4) Inorganic flame retardant

A) Aluminum hydroxide (trade name: “BF013”, manufactured by Nippon LightMetal Company, Ltd., average particle diameter: 1.2 μm)

B) Magnesium hydroxide (trade name: “MAGSEEDS N6”, manufactured byKonoshima Chemical Co., Ltd.)

C) Calcium hydroxide (manufactured by Yoshizawa Lime Industry CO., LTD.)

Subsequently, the flame retardant resin composition was kneaded for 15minutes at 160° C. by using a Banbury mixer. Thereafter, this flameretardant resin composition was fed into a single screw extruder(L/D=20, screw type: full flight screw, manufactured by Marth Seiki Co.,Ltd.), and a tube-shaped extrusion product was extruded from theextruder and coated on a conductor (number of strands:one/cross-sectional area: 2 mm²) to have a thickness of 0.7 mm. Thus, aninsulated wire was obtained.

TABLE 1 Comparative Comparative Example 1 Example 1 Example 2 Example 3Example 4 Example 5 Example 2 Resin Base resin PE 97 97 97 97 97 97 97composition Silicone- Silicone MB (PE/silicone) 3/3 3/3 3/3 3/3 3/3 3/33/3 based compound Fatty acid Mg stearate 5 5 5 5 5 5 5 containingcompound Inorganic Aluminum hydroxide 3 5 10 20 25 40 50 flame retardantDecomposition onset Inorganic flame retardant 220 220 220 220 210 210220 temperature [° C.] (T3) Silicone-based compound 300 290 300 300 300300 300 (T1) Base resin (T2) 450 450 450 460 460 450 450 Flameretardancy Vertical Pass 60 80 100 100 100 80 10 combustion test rate(%) Mechanical property Tensile strength (MPa) 20.8 20.6 20.4 16.4 17.814.8 13.3

TABLE 2 Comparative Comparative Example 3 Example 4 Example 6 Example 7Example 8 Resin Base resin PE 100 99 98.5 90 85 compositionSilicone-based Silicone MB (PE/silicone) 1/1 1.5/1.5 10/10 15/15compound Fatty acid Mg stearate 5 5 5 5 5 containing compound Inorganicflame Aluminum hydroxide 20 20 20 20 20 retardant Decomposition onsetInorganic flame retardant (T3) 200 210 200 230 200 temperature [° C.]Silicone-based compound — 300 300 290 310 (T1) Base resin (T2) 450 440450 470 460 Flame retardancy Vertical Pass rate (%) 0 0 100 100 100combustion test Mechanical property Tensile strength (MPa) 20.0 20.419.7 16.2 12.1

TABLE 3 Comparative Example 5 Example 9 Example 10 Resin compositionBase resin PE 97 97 97 Silicone-based Silicone MB (PE/silicone) 3/3 3/33/3 compound Fatty acid containing Mg stearate 2 10 20 compoundInorganic flame Aluminum hydroxide 20 20 20 retardant Decompositiononset temperature [° C.] Inorganic flame retardant (T3) 210 200 210Silicone-based compound (T1) 600 290 310 Base resin (T2) 450 450 470Flame retardancy Vertical Pass rate (%) 0 100 100 combustion testMechanical property Tensile strength (MPa) 18.2 16.8 16.2

TABLE 4 Example 11 Example 12 Example 13 Example 14 Resin Base resin PE97 composition EEA 97 EVA 97 PP 97 Silicone-based Silicone MB(PE/silicone) 3/3 3/3 3/3 3/3 compound Fatty acid Mg stearate 5 5 5containing compound Ca stearate 10 Inorganic flame Aluminum hydroxide 2020 20 20 retardant Decomposition onset temperature [° C.] Inorganicflame retardant (T3) 210 200 210 230 Silicone-based compound (T1) 290310 300 390 Base resin (T2) 430 420 470 460 Flame retardancy VerticalPass rate (%) 100 100 100 100 combustion test Mechanical propertyTensile strength (MPa) 17.1 23.3 22.1 18.5

TABLE 5 Comparative Comparative Example 6 Example 7 Resin Base resin PE97 97 composition Silicone-based Silicone MB (PE/silicone) 3/3 3/3compound Fatty acid Mg stearate 5 5 containing compound Inorganic flameAluminum hydroxide retardant Magnesium hydroxide 20 Calcium hydroxide 20Decomposition onset temperature [° C.] Inorganic flame retardant (T3)350 400 Silicone-based compound (T1) 290 270 Base resin (T2) 460 450Flame retardancy Vertical Pass rate (%) 0 0 combustion test Mechanicalproperty Tensile strength (MPa) 18.5 16.5

For the insulated wires of Examples 1 to 14 and Comparative Examples 1to 7 obtained as described above, evaluation of the flame retardancy andthe mechanical property was made as described below.

<Flame Retardancy>

Ten insulated wires were prepared for each of Examples 1 to 14 andComparative Examples 1 to 7. Then, a single vertical combustion test wasperformed for those wires based on JIS C3665-1, and the flame retardancywas evaluated. Specifically, when the length between the lower end ofthe upper supporting member, which supports the insulated wire at thetop, and the end point of carbonization is 50 mm or more and 540 mm orless, it is graded as “pass”, and the length less than 50 mm or morethan 540 mm is graded as “failure.” Then, the pass rate (%) wascalculated. The results are shown in Tables 1 to 5. Meanwhile, in thecombustion test, the insulated wire was brought into contact with burnerflame for 60 seconds. Furthermore, in Tables 1 to 5, the criteria forevaluating the pass or failure in terms of the flame retardancy is asfollows.

Pass rate of 70% or more: Pass

Pass rate of less than 70%: Failure

<Mechanical Property>

The evaluation of the mechanical property for the insulated wires ofExamples 1 to 14 and Comparative Examples 1 to 7 was performed based onthe tensile strength that is measured by tensile test according to JISC3005. The results are shown in Tables 1 to 5. In Tables 1 to 5, theunit of the tensile strength is MPa, and the criteria for evaluating thepass or failure in terms of the tensile strength is as follows. In thetensile test, the elongation rate was 200 mm/min and the distancebetween surface lines was 20 mm.

10 MPa or more: Pass

Less than 10 MPa: Failure

From the results of Tables 1 to 5, the insulated wires of Examples 1 to14 satisfied the pass criteria in terms of the flame retardancy and themechanical property. In contrast, the insulated wires of ComparativeExamples 1 to 7 did not satisfy the pass criteria in terms of at leastone of the flame retardancy and the mechanical property.

In view of the above, it was confirmed that the flame retardant resincomposition of the invention can secure excellent flame retardancy whilesecuring an excellent mechanical property.

EXPLANATIONS OF NUMERALS

-   -   1 INTERNAL CONDUCTOR    -   2 INSULATING LAYER    -   3, 25, 35 SHEATH    -   4 INSULATED WIRE    -   10, 20, 30 CABLE

The invention claimed is:
 1. A flame retardant resin compositioncomprising: a polyolefin resin; a silicone-based compound blended at aratio of 1.5 parts by mass or more and 20 parts by mass or less relativeto 100 parts by mass of the polyolefin resin; a fatty acid containingcompound blended at a ratio of 5 parts by mass or more and 20 parts bymass or less relative to 100 parts by mass of the polyolefin resin; andan inorganic flame retardant blended at a ratio of 5 parts by mass ormore and 40 parts by mass or less relative to 100 parts by mass of thepolyolefin resin, wherein the decomposition onset temperature of theinorganic flame retardant is lower than the decomposition onsettemperature of the silicone-based compound, and wherein the differencebetween the decomposition onset temperature in helium of the inorganicflame retardant and decomposition onset temperature in helium of thesilicone-based compound is more than 0° C. and 250° C. or less; whereinthe composition consists of the polyolefin resin, the silicone-basedcompound, the fatty acid containing compound, the inorganic flameretardant, and at least one additive selected from the group consistingof an oxidation inhibitor, an ultraviolet ray deterioration inhibitor, aprocessing aid, a coloring agent, and an anti-static agent; theoxidation inhibitor is formed of at least one selected from the groupconsisting of a phenol-based oxidation inhibitor, an amine-basedoxidation inhibitor, a sulfur-based oxidation inhibitor, aphosphorus-based oxidation inhibitor, a hydrazine-based oxidationinhibitor, an amide-based oxidation inhibitor, phosphoric acid, andcitric acid, the ultraviolet ray deterioration inhibitor is formed of atleast one selected from the group consisting of a benzophenone-basedultraviolet ray deterioration inhibitor, a salicylate-based ultravioletray deterioration inhibitor, a benzotriazole-based ultraviolet raydeterioration inhibitor, an acrylonitrile-based ultraviolet raydeterioration inhibitor, a metal complex salt-based ultraviolet raydeterioration inhibitor, and a hindered amine-based ultraviolet raydeterioration inhibitor, the processing aid is formed of at least oneselected from the group consisting of a hydrocarbon-based processingaid, a fatty acid-based processing aid, a fatty acid amide-basedprocessing aid, an ester-based processing aid, an alcohol-basedprocessing aid, a metal soap, and wax, the coloring agent is formed ofat least one selected from the group consisting of an inorganic pigment,an organic pigment, and a dye, and the anti-static agent is formed of atleast one selected from the group consisting of a cationic active agent,an anionic active agent, a non-ionic active agent, and an amphotericactive agent.
 2. The flame retardant resin composition according toclaim 1, wherein the inorganic flame retardant is aluminum hydroxide. 3.The flame retardant resin composition according to claim 1, wherein theinorganic flame retardant is blended at a ratio of 10 parts by mass ormore and 25 parts by mass or less relative to 100 parts by mass of thepolyolefin resin.
 4. The flame retardant resin composition according toclaim 1, wherein the fatty acid containing compound is magnesiumstearate or calcium stearate.
 5. A cable comprising an insulated wirewhich has a conductor and an insulating layer covering the conductor,wherein the insulating layer is formed of the flame retardant resincomposition according to claim
 1. 6. A cable having a conductor, aninsulating layer covering the conductor, and a sheath covering theinsulating layer, wherein at least one of the insulating layer and thesheath is formed of the flame retardant resin composition according toclaim
 1. 7. A cable having a sheath and an optical fiber provided on theinner side of the sheath or provided to penetrate the sheath, whereinthe sheath is formed of the flame retardant resin composition accordingto claim
 1. 8. The flame retardant resin composition according to claim1, wherein the decomposition onset temperature of the silicone-basedcompound is lower than the decomposition onset temperature of thepolyolefin resin.
 9. The flame retardant resin composition according toclaim 8, wherein the difference between the decomposition onsettemperature in helium of the silicone-based compound and thedecomposition onset temperature in helium of the polyolefin resin is 100to 250° C.
 10. The flame retardant resin composition according to claim1, wherein the difference between the decomposition onset temperature inhelium of the inorganic flame retardant and decomposition onsettemperature in helium of the silicone-based compound is 50 to 250° C.11. The flame retardant resin composition according to claim 10, whereinthe difference between the decomposition onset temperature in helium ofthe inorganic flame retardant and decomposition onset temperature inhelium of the silicone-based compound is 50 to 150° C.
 12. The flameretardant resin composition according to claim 1, wherein the differencebetween the decomposition onset temperature in helium of the inorganicflame retardant and decomposition onset temperature in helium of thesilicone-based compound is more than 0° C. and 150° C. or less.
 13. Theflame retardant resin composition according to claim 12, wherein when anEGA thermogram is measured at the following conditions by using athermal analysis and gas chromatograph-mass spectrometry in which asample loading part equipped with a thermal decomposition device and agas chromatograph-mass spectrometry are connected to each other via acapillary tube made of SUS, the decomposition onset temperature is atemperature which corresponds to a peak rising point with respect to abaseline in the thermogram: temperature increasing rate in thermaldecomposition device is 50° C./min, temperature range is 70 to 700° C.,column oven temperature is 320° C., carrier gas is helium, pressure is90.0 kPa, and column flow rate is 0.92 mL/min.
 14. The flame retardantresin composition according to claim 12, wherein the difference betweenthe decomposition onset temperature in helium of the inorganic flameretardant and decomposition onset temperature in helium of thesilicone-based compound is more than 0° C. and 110° C. or less.